Digital cameras (inclusive of digital still cameras, digital movie cameras and mobile telephones equipped with a digital camera) include those that track a target image. For example, there is one that sets multiple windows within a display screen, measures distance for every window and performs tracking based upon the measured values (Patent Document 1), one that detects an object to be tracked by comparing an image captured now and the image captured last (Patent Document 2), and one that performs tracking by changing, in accordance with distance and shooting-lens focal distance and the like, the size of a zone that captures, as a reference pattern, the image of a target subject to be tracked (Patent Document 3).
In a case where a target image is tracked, it is necessary to set the target image. Often the setting of the target image is performed by having the user designate the target image. However, when an attempt is made to designate a featureless, difficult-to-track image, tracking is difficult to carry out. For this reason, there is system that decides the initial position of a tracking frame (Patent Document 4).
[Patent Documents]
[Patent Document 1]: Japanese Patent Application Laid-Open No. 5-52562
[Patent Document 2]: Japanese Patent Application Laid-Open No. 2005-114588
[Patent Document 3]: Japanese Patent Application Laid-Open No. 2006-184742
[Patent Document 4]: Japanese Patent Application Laid-Open No. 2011-160062
With the arrangement described in Patent Document 1, something at a short distance is always selected when a tracking window is set. In a case where an object is on this side of the target, therefore, the object cannot be tracked. With the arrangement described in Patent Document 2, an object is assumed to be one whose central portion projects forward, with the result that an object other than such an object tends not to be tracked. With the arrangement described in Patent Document 3, the setting of the tracking target is left up to the user. In a case where the user sets a featureless portion as the target, therefore, there are instances where it cannot be tracked. Furthermore, with the arrangement described in Patent Document 4, the initial position of a tracking frame is decided within a target area for setting the initial position of the tracking frame. If the target area is large, however, it takes time to decide the initial position of the tracking frame.